1. Field of the Invention
The present invention is in the field of processes for the recovery of metal values from solution followed by pyrometallurgical treatment of the cementate and ultimate recovery of the metal in relatively pure form.
2. Description of the Prior Art
Cementation processes have been carried out in an oscillating container filled at least partially with pieces of a cementation medium as shown, for example, in German Laid Open Specification No. 24 57 660. In this publication, there is a disclosure of precipitating copper cement from a copper solution mixed with iron pieces as a precipitant. The iron pieces are shaken in an oscillating reactor with suitable frequency and amplitude so that the pieces of iron constantly rub against each other and the copper which is constantly being precipitated on the cementation medium in the form of a coating is continually scoured off the surfaces of the iron pieces. With this type of arrangement, using a constant substantial voltage potential between the iron and copper solution, the cementation may be completed rapidly and without hindrance.
A similar method has been described in German Patent Specification No. 26 02 849 wherein both the leaching process as well as the precipitation process is carried out simultaneously in the same reaction vessel. In this procedure, the oscillating bodies are, for example, crude iron granulates, stamping waste, and other bodies such as cast metal scrap, pig iron, or puddled iron.
In known cementation methods, for example, the known GLPF method (Grinding, Leaching, Precipitating, Flotation), the relatively pure cement metal recovered after the flotation was usually subjected to a pyrometallurgical melting process. The cementate was preferably melted under reducing conditions, while the cementation medium such as for example iron or zinc was converted by means of addition of slag formers such as sand, limestone, and the like into a slag phase. Such slags, however, contain significant residual contents of the metal values from the cementate. These slags were previously disposed of as tailings or, after comminution and grinding, treated additionally for the recovery of the metal values. In either event, there are appreciable losses in residual metal or substantial additional costs involved.